A high-level Chinese GlaxoSmithKline PLC executive appeared to back allegations of bribery in an interview on state-controlled television in China on Tuesday, as Beijing ratcheted up pressure on the U.K. drug maker.

China's powerful state-run broadcaster on late Monday and Tuesday aired an interview with Liang Hong, Glaxo's China vice president and operations manager, who is one of four Chinese executives detained as part of a Chinese bribery probe into the company. Mr. Liang described for viewers of China Central...